feat: TFT display init and splash screen

Landscape 160x80 (rotation 3, no invert) per this panel.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

WeatherPredictor/WeatherPredictor.ino

@@ -1,6 +1,7 @@
 #include <Arduino.h>
 #include <Wire.h>
 #include "config.h"
+#include "display_ui.h"
 
 static void i2cScan() {
   Serial.println(F("I2C scan:"));
@@ -21,6 +22,9 @@ void setup() {
   Serial.println(F("\n=== Weather Predictor booting ==="));
   Wire.begin(I2C_SDA, I2C_SCL);   // MUST come before any I2C driver begin()
   i2cScan();
+
+  displayBegin();
+  displaySplash("Weather", "Predictor v0.1");
 }
 
 void loop() {